Did I only mention my husband's bad points? My bad...
He has many, many good points and I'm pretty sure that this whole episode was a bad blip. I think he is going through a serious life crisis. At the time of the miscarriage we were on two totally different planets and we didn't get to reconnect until after I found out about the other women. It is hard to give up on a relationship that has lasted more than a quarter of your life... so many memories, small children together, and all the work that goes into keeping a relationship together over time. In my mind, I married for life.
I'm with you on the time aspect redpepper... how is it possible to have children AND have time for more lovers?! I guess my husband is on the road a lot so there will be time then.
He read all your posts by the way: I think that was a pretty sobering experience for him. So far he had managed to avoid the opinion of his peers by saying 'they're in a monogamous mindset so they can't possibly understand.' Opening this up to other poly voices was a good idea.

For the time being, we are going strong. He has accepted my ultimatum, we are going to open our relationship to other people (nice folk, no vampires) and we'll see! I feel good that I stood up for something that I couldn't accept.

A BIG THANK YOU to all the people who took the time to respond to my post!